Dispersion of microcapsules for the improved thermochromic performance of smart coatings

Abstract

Microcapsules are widely applied in coatings; however, there are very few reports on the dispersion of microcapsules in the coating material or the effects of dispersion on their performance. Herein, the efficiency of three types of dispersants bearing distinctive functional groups for the dispersion of concentrated thermochromic microcapsules in a solvent and coating resin is studied. The dispersion properties of 35 wt% thermochromic microcapsules in toluene and in coating resin are investigated by measuring their sedimentation and rheological behavior. Interactions between the dispersant and microcapsules are characterized by Fourier transform infrared spectroscopy in order to identify the dominant dispersion mechanism. The physical quality and thermochromic performance of the coating films are characterized by electron microscopy observations and temperature variation tests. The most effective dispersant for thermochromic microcapsules is determined. Compared to the coating film containing non-dispersed microcapsules, the film with well-dispersed microcapsules shows improved surface flatness, with few or no pores in the microstructure. In addition, the color of the film with well-dispersed thermochromic microcapsules shows faster response to temperature variation, resulting in complete and uniform color transformation.